The inventive concepts described herein relate to a semiconductor memory, and more particularly, relate to a nonvolatile memory device.
A semiconductor memory device is a storage device which is fabricated using semiconductors such as, but not limited to, silicon (Si), germanium (Ge), gallium arsenide (GaAs), and indium phosphide (InP). Semiconductor memory devices are classified into volatile memory devices and nonvolatile memory devices.
The volatile memory devices may lose contents stored therein at power-off. Volatile memory devices include the following: a static RAM (SRAM), a dynamic RAM (DRAM), and a synchronous DRAM (SDRAM). The nonvolatile memory devices may retain stored contents even at power-off. Nonvolatile memory devices include the following: a read only memory (ROM), a programmable ROM (PROM), an electrically programmable ROM (EPROM), an electrically erasable and programmable ROM (EEPROM), a flash memory device, a phase-change RAM (PRAM), a magnetic RAM (MRAM), a resistive RAM (RRAM), and a ferroelectric RAM (FRAM). The flash memory is classified as a NOR type or a NAND type.
A three-dimensional semiconductor memory device of a three-dimensional array structure is being researched to improve the degree of integration of a semiconductor memory. The height of the three-dimensional semiconductor memory device continues to increase. When a distance between a peripheral circuit and a pad increases, resistance and capacitance also increase, thereby making response speed of the three-dimensional semiconductor memory device slow.